Calibrating radiocarbon ages with tree ring ages
Page 8 of 12

Before applying the C-14 method to some newly discovered "materials", we need to examine one of its assumptions: that the amount of C-14 produced in the Earth's upper atmosphere from cosmic rays striking N-14 is constant over time. It turns out that the production of C-14 changes somewhat from year to year because of variations in incoming cosmic radiation. Increased solar flare activity increases C-14 with higher amounts of C-14 found in organisms that lived during those times.

To compensate for variations in C-14, scientists have developed calibration curves from studies of tree rings of the ancient Bristlecone Pines of the White Mountains of California and oak trees of Germany and Ireland. Through these studies (dendrochronology), calibration data has been developed that goes back nearly 11,000 years.

The applet below compares actual tree ring ages (from counting) with the equivalent Radiocarbon age. Use your mouse to drag on the wood core to set the variation tree rings between 1000 to 400 years old.

Answer these questions then go on to see the calibration curves that have been constructed from these kinds of observations.
1. What is the measured C-14 age of Bristlecone wood that is 900 years old?
2. A C-14 age greater than the ring age implies that the amount of C-14 in the atmosphere at that time was____  
  greater than normal less than normal no way to tell  
3. What is the measured C-14 age of Bristlecone wood that is 450 years old?
4. A C-14 age that is less than the ring age implies that the amount of C-14 in the atmosphere at that time was____  
  greater than normal less than normal no way to tell  

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